The present invention relates generally to gas turbine engines with counter-rotatable fans and, more particularly, to such engines having axial flow positive displacement gas generators and worm and screw compressors and turbines.
Aircraft gas turbine engines generally have in downstream flow relationship fan, compressor, combustion, and turbine sections. The turbine sections generally drive the compressor and fan sections. The combustor section burns fuel in an airflow compressed by the compressor to provide energy to the turbines. Aircraft gas turbine engines may have one, two, three, or more rotors or spools. One or two fans upstream of the compressor are driven by one or two turbines as are the compressors. The fans, compressors, and turbines typically include radially extending blades. Core engines or gas generators of the aircraft gas turbine engine generally include a high pressure compressor, a combustor, and a high pressure turbine to provide high energy fluid to the turbines to provide power for the engine's fan or fans. Continuous axial flow gas turbine engines are utilized in a wide range of applications owing in a great deal to a combination of desirable attributes such as high specific energy exhaust stream (energy per unit mass), high mass flow rate for a given frontal area, continuous near steady fluid flow, and reasonable efficiency over a wide range of operating conditions. It is desirable to have light-weight and highly efficient engines. One type of highly efficient engine includes counter-rotatable fans powered by counter-rotatable low pressure turbines such as those disclosed in U.S. Pat. Nos. 6,763,653, and 6,763,654.
Axial flow gas generators are particularly useful in many turbomachinery applications. Turbomachinery based gas generators are utilized in a wide range of applications owing in a great deal to a combination of desirable attributes such as high specific energy exhaust stream (energy per unit mass), high mass flow rate for a given frontal area, continuous, near steady fluid flow, reasonable thermal efficiency over a wide range of operating conditions. It is a goal of gas turbine engine manufacturers to have light-weight and highly efficient engines and gas generators. It is another goal to have as few parts as possible in the gas generator to reduce the costs of manufacturing, installing, refurbishing, overhauling, and replacing the gas generator. Therefore, it is desirable to have an aircraft gas turbine engine with a gas generator that improves all of these characteristics of gas turbine engines and their gas generators.